Compound Interest Calculator

Einstein allegedly called compound interest the "eighth wonder of the world." Whether he said it or not, the math doesn't lie: time in the market is the most powerful wealth-building tool you have. This calculator shows you exactly how your money grows — and why starting now matters more than starting big.

The Power of Compound Interest

Here's what makes compound interest so powerful: your returns earn returns. In year 1, you earn interest on your principal. In year 2, you earn interest on your principal + year 1's interest. This exponential curve is what makes long-term investing so effective.

A Real Example

Invest $200/month starting at age 25, earning an average 8% annual return:

• At 35 (10 years): $36,580 — you invested $24,000
• At 45 (20 years): $115,000 — you invested $48,000
• At 55 (30 years): $298,000 — you invested $72,000
• At 65 (40 years): $690,000 — you invested $96,000

You put in $96,000 total. You end up with $690,000. $594,000 is pure compound growth. That's the eighth wonder of the world.

Starting Late vs Starting Small

Here's what most people don't realize: starting small beats starting late. Investing $100/month starting at 25 yields more than investing $500/month starting at 35 — because the early money has more time to compound. Time beats amount every single time.

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